Atomistic-scale simulation of multilayer graphene etching induced by H<i>x</i>+ (<i>x</i> = 1−3) ions irradiation in hydrogen plasma

The plasma hydrogenation technique is widely recognized as an efficient tool for modifying graphene’s physical and chemical properties. Therefore, a comprehensive understanding of the interaction between plasma and graphene at the atomic scale can provide valuable insights into the potential applications of graphene. Here, using MD (molecular dynamics) simulations and the existence of different ionic species in hydrogen plasma, we investigate the multilayer graphene etching process under Hx+(x=1-3) ion irradiation. The ion energy range is chosen between 2.5 and 40 eV. It is shown that for all three ion species at the lower energy, ions cannot penetrate the lower layers, and hydrogenation of graphene increases with ion fluence until it reaches saturation. At higher energies, ions can penetrate and etching can be observed for all three ionic species. Among these species, the H2+ ion exhibits the fastest initiation of etching on the top layer. Due to the higher observed percentage of an H3+ ion in some hydrogen plasmas and the dependency of the energy barrier for hydrogen chemisorption in graphene on the number of layers, we also consider a wide range of energies for an H3+ ion and investigate one- and four-layer graphene irradiated by H3+ ions. It is seen that the hydrogenation rate of one-layer graphene is lower than four-layer graphene, and the etching process begins at an energy of ≈20 eV. It is also indicated that the etching initiates at lower ion doses by increasing the energy of the H3+ ion.